1. Field of the Invention
The present invention relates generally to apparatus for heating water or the like, and more particularly, to the construction of heat exchange tubes of the type which carry hot combustion gases therethrough for heat exchange with water or the like flowing around the outside of the tube.
2. Description of the Prior Art
Traditionally heat exchangers, particularly condensing fire tube heat exchangers, have utilized a tube bundle made up of a plurality of relatively small diameter cylindrical tubes extending between an inlet tube sheet and an outlet tube sheet. Typically those tubes have been of a diameter in the range of from ½ to ¾ of an inch. This has required the use of a large number of tubes within a tube bundle to achieve the necessary heat exchange between hot combustion gases and the water or other fluid flowing around the tubes. The use of relatively large numbers of relatively small diameter tubes leads to a substantial effort and expense in welding all of the tubes in place within their respective tube sheets.
There is a need for improved designs for the heat exchange tubes for fire tube heat exchangers.